As the current semiconductor technology poses a continuous demand for higher density packaging and reductions in size, weight and profile of semiconductor packages, the number of interconnections is increasing. Accordingly, finer pitches are set between aluminum pattern interconnections or gold wires on the chip surface. In particular, the pitch between gold wires, which is more than 100 μm in the past, is now narrowed to 50 μm or less and will reach 30 μm or less. When such a fine pitch interconnection device is encapsulated with an encapsulant, the flowing encapsulant can cause damages to gold wires, often inviting molding defects such as flow, deformation, and breakage of gold wires. In connection with fine pitch interconnection devices, it would be desirable to have a semiconductor-encapsulating composition which prevents gold wires from being flowed or broken during molding and minimizes the occurrence of leak failure between gold wires, and a semiconductor package having such advantages.
With respect to the problem of leak failure, in particular, several approaches are taken to tailor carbon black, including coating carbon black particles with a resin for insulation, dry classification of starting carbon black powder through a sieve to cut off a coarse fraction, and disintegration of coarse particles by pre-milling into finer particles. All these approaches have drawbacks from the standpoints of process efficiency and effective removal of a coarse fraction.
Typical encapsulants used with fine pitch interconnection devices are epoxy resin compositions based on low melt viscosity epoxy resins. When such low viscosity epoxy resin compositions are prepared, it is unlikely that sufficient torques are applied to the mass during kneading, which conditions are deleterious to the dispersion of carbon black. An attempt is also made to use an organic dye to prevent the occurrence of leak failure between gold wires. However, the dye is insufficient in heat resistance and color, failing to overcome the problems.
Known references pertinent to the present invention include JP-A 2006-282700, JP-A 2006-89670, JP-A 2005-112880, JP-A 2005-36062, JP-A 2004-269636, JP-A 2003-337129, and JP-A 2001-354837.